1. Field of the Invention
The present invention relates generally to displays and, more particularly, to a display having an improved frame surrounding a display element.
2. Description of the Background Art
A display to be applied to a digital switch and the like comprises a display element for displaying numerals, a printed wiring board on which a circuit element for the display element is mounted, and a casing for accommodating the display element and the printed wiring board. A display window is provided in this casing, and the display element is provided in the casing with its display face facing the display window.
With a portion of a human body electrostatically charged with frictional electrification being in proximate to or in contact with such a display, when a charge enters through the display window to the inside of the casing, the circuit element mounted on the printed wiring board is liable to be destroyed by the charge. In order to protect the circuit element, in the display of the background art of the present invention, provision of a metal frame attached onto the periphery of the display window of the casing and further provision of a ground lead within the casing to contact this metal frame causes the charge, which entered in the display, to flow out of the display through the metal frame and the ground lead.
However, there were disadvantages of increases in the number of components and assemblies and in production cost since the metal frame is employed as described above. Further, it sometimes occurs that the metal frame is deformed by some external force in assembly of the display. Moreover, even if no abnormality occurs in the assembly of the display, a poor contact between the metal frame and the ground lead in use causes a charge to be stored in the display, leading to a fear of destruction of the circuit element.
In addition, the display of the background art of the present invention involves another disadvantage that due to a gap between the display window and the display element, even if a filter is attached to the display window, the printed wiring board located at the peripheral portion of the display element can be viewed through the filter, resulting in the unattractive display in appearance.